Method for manufacturing medical articles composed of various synthetic high polymers coated with collagen and exposed to radiation

ABSTRACT

MEDICAL ARTICLES COMPOSED OF A SYNTHETIC HIGH POLYMER COATED WITH COLLAGEN TO BE USED IN A LIVING BODY ARE MANUFACTURED BY SUBJECTING A SURFACE OF SHAPED ARTICLES COMPOSED OF THE SYNTHETIC HIGH POLYMER OF POLYETHYLENE, POLYPROPYLENE, POLYETHYLENE TEREPHTHALATE, TEFLON OR SILICONE RESIN TO A SPARK DISCHARGE, COATING THE THUS TREATED SURFACE WITH AN ACIDIC AQUEOUS SOLUTION OF COLLAGEN AND THEN DRYING SAID SURFACE TO FORM COLLAGEN LAYER AND IRRADIATING THE SHAPED ARTICLE COATED WITH COLLAGEN WITH RADIOACTIVE RAYS, ELECTRON BEAM OR ULTRAVIOLET RAY UNDER AN ATMOSPHERE HAVING SUCH A HUMIDITY THAT THE WATER CONTENT OF THE COATED COLLAGEN BECOMES MORE THAN 20% BY WEIGHT.

sElzo OKAMUR` ETAL 3,808,113

Apri13o,1974 l METHOD FOR MANUFACTURING MEDICAL ARTICLES COMPOSED 0F'VARIOUS SYNTHETIC HIGH POLYMERS COATED WITH COLLAGEN AND EXPOSED TORADIATION 4 Sheets-Sheet 1 Filed July 50, 1971 E F N .L l- .M V/ y r4 KwA m Wm n, a

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METHOD FOR MANUFACTURING MEDICL ARTICLES COMPOSED OF VARIOUS SYNTHETICHIGH POLYMERS COATED WITH v COLLGEN'AND EXPOSED TO RADIATION Filed July30, 1971 l 4 Sheets-Sheet n 4,5. y 7 ...,f, P/ PAW/1 1 f a f.. m4, L an4.. ivy/f B. M W., /l 5 .W 4 6 M W f/ fw M .y M f f f 0/6 p/AM 4@ 4m 5N/ M j o 0 o o ,14" L n 0 a f M .w ywm sElzo QKAMURA ETAL 3,808,113-

April 30, 1974 y METHOD FOR MANUFACTURING MEDICAL ARTICLES COMPOSED OFVARIOUS SYNTHETIC HIGH POLYMERS COATED WITH COLLAGEN AND ExPosED roRADIATION v 4 Sheets-Sheet I5 Filed July 30, 1971 M vl am 544 7 C x 0 Dw C 5 /wv A v 6 mi M fr a .A y w I W0 WIM b: J.. Il l. x 1.x.. .0 0 d 0.w 7 a w 4 :ad a. m

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METHOD FR MANUFACTURING MEDICAL ARTICLES COMPOSED OF VARIOUS SYNTHETICHIGH POLYMERS COATED WITH A COLLAGEN AND EXPOSED T0 RADIATION Filed July50, 1971 4 Sheets-Sheet 4 United States Patent Office 3,808,1 13Patented Api'. 30, 1974 3,808,113 METHOD FOR MANUFACTURING MEDICALARTICLES COMPOSED OF VARIOUS SYN- THETIC HIGH POLYMERS COATED WITHCOLLAGEN AND EXPOSED TO RADIATION Seizo Okamura, Kyoto, and TsunetoshiHino, Higashi- Osaka, Japan, assignors to Zaidan Hojin: Seisan KaihatsuKagaku Kenkyusho, Kyoto, Japan Filed July 30, 1971, Ser. No. 167,850Claims priority, appliscation Japan, Aug. 6, 1970,

U.S. Cl. 20d- 159.12 7 Claims ABSTRACT OF THE DISCLOSURE Medicalarticles composed of a synthetic high polymer coated with collagen to beused in a living body are manufactured by subjecting a surface of shapedarticles composed of the synthetic high polymer of polyethylene,polypropylene, polyethylene terephthalate, Tefion or silicone resin to aspark discharge, coating the thus treated surface with an acidic aqueoussolution of collagen and.

then drying said surface to form collagen layer and irradiating theshaped article coated with collagen with radioactive rays, electron beamor ultraviolet ray under an atmosphere having such a humidity that thewater content of the coated collagen becomes more than 20% by weight.

( l) no toxicity and carcinogenic property (2) no antigenic-antibodicproperty (3) no coagulation of blood (4) afiinity to the living bodyRecently, synthetic high polymeric materials have been used in medicalfield and particularly various synthetic high polymers, such aspolyethylene, polypropylene, polyethylene terephthalate, Teflon(trademark of polytetrafluoroethylene made by E. I. du Pont de Nemours &Co. Inc.), silicone resin and the like have been used to form artificialblood vessels, artificial organs, blood ducts, and blood container.However, the medical articles to be used in a living body, which aremanufactured from the above described various synthetic high polymers,cannot satisfy the above described requirements fully.

It has been said that polyethylene, polyethylene terephthalate, Teflon,silicone resin, etc. among the various synthetic high polymers haverelatively favorable properties as the materials for medical articles tobe used in a living body and among them silicone resin has a resistanceto coagulation of blood and suits for medical articles to be used in aliving body and for example, a surface treating agent composed of liquidsilicon which is used as a coating agent for medical articles, iscommercially available but it is not complete and when using in a livingbody an agent for preventing coagulation of blood having a highactivity, such as heparin should be used together.

It has been proposed to use collagen, Iwhich is one kind of highpolymers constituting a living a body, as a material for medical articleto be used in a livingbody.

Collagen is obtained in a water soluble form and such a process isdisclosed in U.S. Pat. No. 3,034,852 and No. 3,530,037. Collagen has acompatibility to the living body and the purified collagen in whichtelopeptide in the end of molecule is removed by an enzyme treatment hasno antigenicity and has a high afiinity to heparin, so that the collagenis suitable for material of medical articles to be used in a livingbody.

However, the above described collagen is insufficient in the mechanicalstrength and elasticity and it is difiicult to use collagen as a singlematerial for producing the above described medical articles, such asartificial blood vessels and artificial organs.

The inventors have studied the materials for producing said medicalarticles in view of the synthetic high polymers and high polymersconstituting the living body and noticed that if the medical articlescomposed of synthetic high polymers, the surface of which is coatedtightly with collagen, can be manufactured, such medical articles cansatisfy all the above described four requirements necessary for themedical articles to be used in living body and various investigationshave been made with respect to such articles for a long time.

However, as well-known, the surface of the shaped articles of thesynthetic high polymers, such as polyethylene, polyethyleneterephthalate, silicone resin and the like is non-polar or substantiallynon-polar and is chemically stable and it has been difficult to coat thesurface of said polymer with collagen tightly.

The inventors have made various investigations in o1'- der to develop aprocess by which collagen is coated tightly on the surface of themedical articles composed of synthetic high polymers, such aspolyethylene, polyethylene terephthalate, Tefion, silicone resin and thelike and the present invention has 'been accomplished.

The inventors have attempted such a means that the surface of the shapedarticles of synthetic high polymers is firstly treated with knownchemical agents, for example, acids, alkalis, chromic acid mixture andphosphorus trichloride or graft polymerized with a reactive differentmonomer, for example, maleic anhydride, vinyl ether, etc., and thenapplied with an aqueous solution of collagen and the applied surface isdried and then irradiated with qf-ray, whereby the surface of the'shapedarticle is coated with collagen tightly.

By the above described means, the peel off strength of collagen is 1,000g./cm. for polyethylene, while for silicone resin, a satisfactory peelofi` strength is not shown.

The medical articles which are used in direct contact with living bodymust satisfy the above described requirements and it is not tolerated tocontain even a slight amount of impurities. Accordingly, in the abovedescribed means, that is, the surface treatment with the chemical agentor the surface graft polymerization, there is a fear of incorporation ofimpurities and such -means are not proper.

Furthermore, in these means the optimum process varies depending uponthe synthetic high polymers and these means are troublesome and it isdifiicult to apply these means in a certain shape of shaped articles andin this point these means are not proper.

The inventors have made experiments systematically with respect to theother means and found that spark discharge is most preferable as thesurface treatment and further made investigations with respect to anirradiation of radioactive rays, such as 'y-ray, etc., as a means forforming a thin film of collagen. As the results, the method of thepresent invention has been accomplished by combining these means,wherein collagen can be coated tightly on silicone resin as well as onpolyethylene and the method can be applied to the other synthetic highpolymers and further there is no fear of incorporation of irnpuritiesduring the treating steps.

The present invention consists in a method of manufacturing medicalarticles composed of various synthetic high polymers coated withcollagen, in which a surface of shaped articles composed of a synthetichigh polymer selected from the group consisting of polyethylene,polypropylene, polyethylene terephthalate, Teflon, and silicone resin issubjected to a spark discharge, the thus treated surface is coated withan acidic aqueous solution of collagen and then dried at a temperatureof lower than the denaturation temperature of collagen and the shapedarticle coated with collagen is irradiated with radioactive rays,electron beam or ultraviolet ray under an atmosphere having such ahumidity that the water content of the coated collagen becomes more than20% by weight.

A detailed explanation Will be made concerning the first step of thespark discharge.

'Ihe surfaces of shaped articles, such as film, pipe, tube, fiber,sponge, container and the like, composed of the synthetic high polymerselected from the group consisting of polyethylene, polypropylene,polyethylene terephthalate, Teflon and silicon resin, are cleansed in aconventional manner and subjected to a spark discharge.

The spark discharge maybe effected in air at room temperature and doesnot need a special atmosphere but the end of discharged spark must bealways moved while contacting with the surface to be treated so that theentire surface is uniformly treated.

As the apparatus for spark discharge, use may be made of variousdischarging apparatus and, for example, Tesla Coil type dischargingapparatus is used and the use of the 'generated spark discharge of ahigh frequency is convement. The amount of discharge is controlled bythe length of the discharged spark and the discharge time per area ofthe treated surface and the final point of the discharge treatment isdetermined by the angle of contact formed by the treated surface and thewater drop fallen on the treated surface or the area where a givenamount of water drop occupies the treated surface.

The most important point in this step is the spark discharge conditionand the inventors have made numerous experiments with respect to therelation of the spark discharge conditions to the discharge effect andfound that a simple relation equation is established between the lengthof spark, discharge time and discharge effect and the optimum sparkdischarge conditions have been accomplished based on the novelacknowledge.

Namely, the inventors set the length of spark to 1 cm., 2 cm., 3 cm. and4 cm. and said sparks were applied to the surface of the shaped articlescomposed of synthetic high polymers for the same time per unit area andfurther said sparks were applied to the surface of the shaped articlesby varying the discharge time and the wetting degree of water on thetreated surface or the variation of the variation of infrared spectrumof the treated surface was determined as the indication of the dischargeeffect. As the results, it has been found that when the length of sparkis represented by L cm., the discharge time per unit area is representedby T see/cm.2 and the discharge effect is represented by E, thefollowing relation equation is approximately established wherein k is aconstant.

The discharge effect is proportioned to the product of the length ofspark and the discharge time per unit area and when the length of sparkis 3 ern., the discharge time 75 is preferred to be 3 to 4 sec./cm.2,when the length of spark is l cm., the discharge time is preferred to be9 to l2 sec./cm.2 and when the length of spark is 2 cm., the dischargetime is preferred to be 4.5 to 6 sec/cm?.

From the above described fact, the optimum condition of spark dischargeis 9 to 12 cm. sec./cm.2. In the case of lower than 9 cm. sea/cm?, thedischarge effect cannot be attained and in the case of more than 12 cm.seo/cm?, the effect does not increase and the synthetic high polymer isdeteriorated.

FIG. l shows the wetting degree (by water) when the surface of filmcomposed of various synthetic high polymers is treated with the sparkdischarge under the same condition and the ordinate shows the wettingdegree and the abscissa shows the discharge time (see/cm?) in the lengthof spark of 3 cm. The wetting degree means S/So.

So: the area where 0.05 ml. of water drop occupies on the non-treatedfilm surface.

S: the area where 0.05 ml. of water drop occupies on the film surfacetreated with the spark discharge.

From FIG. 1, it can be seen that when the length of spark is 3 cm., thedischarge effect reaches the maximum value at the discharge time ofabout 4 seo/cm.2l although there is some difference depending upon thekind of material and that even if the discharge more than 4 sec./ cm.2is made, the increase of the effect cannot be expected.

Then the second step wherein an acidic aqueous solution of collagen iscoated on the surface of the shaped articles composed of synthetic highpolymer, is mentioned hereinafter. The concentration of the acidicaqueous solution of collagen is not limited but in view of handling, theconcentration is preferred to be about 0.05 to 3% by weight. The acidicaqueous solution of collagen is very viscous and it is difficult toproduce a high concentration and even if the solution of a highconcentration is prepared, it is difficult to apply said solutionuniformly on the surface of the shaped articles. On the other hand, whenthe concentration is too low, the collagen layer coated on the surfaceby one time of coating and drying is very thin and pin holes are formedand it is necessary to repeat several times of coating and drying.Accordingly, an aqueous solution having a concentration of collagen ofabout 0.05 to 3% is used in View of handling and if necessary, thecoating and drying are repeated to control the thickness of collagenlayer.

The process for applying an acidic aqueous solution of collagen is ausual coating process and when the form of the shaped article iscomplicated, said shaped article is dipped in the acidic aqueoussolution of collagen. Furthermore, when the form of the shaped articleis a container or a tube and only the inner surface of the shapedarticle is to be coated with collagen an acidic aqueous solution ofcollagen is introduced into the inside of said shaped article anddischarged therefrom.

The thus treated shaped article is dried at a temperature lower than thedenaturation temperature of collagen (the denaturation temperature ofcollagen in water varies depending upon the source of collagen but isabout 30 to 37 C.) to form collagen layer on the surface of the shapedarticle. The drying process is preferably natural drying at about 30 C.or draft drying. The water content of the collagen layer dried by theseprocesses is usually 15 to 18%.

Then the final step, wherein the shaped article composed of a synthetichigh polymer coated with collagen layer is irradiated with radioactiverays, electron beam or ultraviolet ray to fix collagen layer, will beexplained.

The essential requirement in the irradiation of radioactive rays,electron beam or ultraviolet ray is that the irradiation is effectedunder such a condition that the water content of the collagen layer ismore than 20% by weight,

The inventors have studied the physical properties of collagen layerirradiated with radioactive rays, electron beam or ultraviolet raysystematically and found that when the water content of collagen layeris less than 20% by weight in the irradiation of collagen, thedecomposition prefers to the cross-linking and the collagen layer iseasily dissolved in water, while when the water content of collagen ismore than 20% by weight, as the water content increases, thecross-linking proceeds and when the collagen layer is irradiated withsuch rays under an atmosphere having a humidity of 100% or in water, thedecomposed product (degradation products of low molecular weightextracted with water or a diluted acid) is not substantially formed anda cross-linked strong layer is formed.

A part of the experimental results concerning the film prepared from anacidic aqueous solution of collagen is shown.

FIG. 2 shows a relation between a dose of y-ray and an amount ofcollagen extracted from the collagen film with water at 40 C.

FIG. 3 shows a relation between a dose of y-ray and the swelling degreeof the collagen film with water at 40 C.

FIG. 4 shows a relation between a dose of 'y-ray and an amount ofcollagen extracted from the collagen film with N/ 100 HCl aqueoussolution at 40 C.

FIG. 5 shows a relation between a dose of 'y-ray and the swelling degreeof the collagen film with N/ 100 HCl aqueous solution at 30 C. and 40 C.In FIGS. 2 to 5, the experiments were effected in air and nitrogenatmosphere and the curve A shows the irradiation in water (the watercontent in the collagen film is 80 to 90%), the curve B shows theirradiation under an atmosphere having a humidity of 100% (the watercontent in the collagen film is 48 to 52:3%), the curve C shows theirradiation under an atmosphere having a humidity of 75% (the watercontent in the collagen film is 18.2 to 19.2%) and the curve D shows theirradiation under dry atmosphere (the water content of the collagen filmis 3.2 to 3.7%). In FIG. 5, the solid line shows the case of 30 C. andthe broken line shows the case of 40 C.

FIG. 2 shows that when the water content of the collagen film is 3.2 to2.7% in the irradiation with Iy-ray, the amount of substance extractedwith water (decomposed product of collagen) increases as the doseincreases to 105 r., 106 r. and 10FI r. and when the dose becomes 10"r., 100% of collagen film is dissolved off in water. The collagen filmhaving a water content of 18.2 to 19.2% by weight also increases thesubstance extracted with water with the increase of the dose of 'y-ray.While, in the collagen film having a water content of 48 to 52.3%, thesubstance extracted with water appears at a dose of rl r. and thecollagen film having a water content of 80 to 90% is not extracted withwater even at the dose of 10'7 r. v

FIG. 3 shows that when the collagen film is irradiated with 'y-ray, thecollagen film having a water content of 3.2-3.7% increases the swellingdegree of water with the increase of dose of y-ray and when the dose offy-ray becornes 10'7 r., all the collagen films is dissolved off asshown in FIG. 2 and the measurement of swelling degree is impossible.This shows that the cross-linking does not occur at all. The collagenfilm having a water content of 18.2-19.2% decreases the swelling degreeat the dose of Iy-ray of 106 r. and this shows the occurence ofcross-linking but when the dose of y-ray further increases, the swellingdegree increases and this shows that the decomposition of collagenprefers to the cross-linking. On the other hand, the collagen filmhaving a water content of 48-5'2.3% decreases the swelling degree evenat the dose of 'y-ray of 10FI r. and this shows that the cross-linkageis formed effectively. The collagen film having a water content of 80 to90% shows the most favorable cross-linkage.

FIGS. 4 and 5 show the case where the experiments were carried out inthesame manner as described above by 6 using a dilute hydrochloric acid(N/100 HCl) instead of water and the tendency is the same as in FIGS. 2and 3.

From the above described fact, it will be understood that theirradiation must be performed under an atmosphere having a humidity ofmore than which makes the water content of collagen layer more than 20%.As well known, hydrophilic high polymers, such as collagen vary thewater content depending upon the ambient humidity condition andequilibrate to the atmosphere and in the experiment of the inventors thewater content of the co1- lagen film when left to stand in an atmospherehaving a humidity of 75 is 18.2-19.2% and as the humidity increases, thewater content in the collagen film increases.

Then, an explanation will be made with respect to the dose ofradioactive rays, electron beam or ultraviolet ray. Concerning theradioactive rays and electron beam, the range of 1-5 106 r. ispreferable 'as shown in FIGS. 2 to 5. If the dose exceeds this range,the decomposition of collagen increases and when the dose does not reachthis range, the effect to cross-linking of collagen decreases.Concerning ultraviolet ray, the commercially available ultraviolet raylamp may be used and the dose is determined by watt number of theultraviolet ray lamp to be used and the irradiation distance to thematerial to be irradiated and in general, it is preferred to effect theirradiation with a ultraviolet lamp of 4 watt from a distance of 10 cm.for 1.5 hours. Furthermore, it is necessary to adjust the distance ofirradiation and time depending upon the watt number of ultraviolet lamp.

By effecting the above described first, second and third steps, it ispossible to manufacture synthetic high polymers coated tightly withcollagen, which are used for medical articles to be used in living body.

An explanation will be made with respect to the peel ofr strength ofcollagen layer when sheets composed of various synthetic high polymershave been subjected to the above described first, second and thirdsteps.

FIG. 6 shows a relation between the dose `of irradiation and the peeloff strength of collagen layer concerning sheet materials compo-sed ofvarious synthetic high polymers and the ordinate shows the peel ofrstrength and the abscissa shows the dose of 'y-ray.

In this case, the surface of the sheet materials is applied to such adischarge treatment that a spark length is 3 cm. an-d a spark dischargetime is 3 seo/cm?, the thus treated surface is coated with an acidicaqueous solution of collagen, the coated sheet material is dried, theacid is neutralized, the thus treated sheet is washed with water, driedin air and irradiated with 'y-ray by varying the dose under nitrogenatmosphere having a humidity of at 20 C.

FIG. 7 shows a relation between the spark discharge time and the peeloff strength of collagen layer concerning sheet materials composed ofvarious synthetic high polymers and the ordinate shows the peel offstrength and the abscissa shows the discharge time of Tesla discharge ofa spark length of 3 cm. FIG. 7 shows the results when the surface ofsheet materials composed of various synthetic high polymers is appliedto discharge at a given spark length of 3 cm. and varying the dischargetime, the discharged surface is coated with an acidic aqueous solutionof collagen, the coated sheet material is dried, the acid isneutralized, the thus treated sheet is washed with water, the coatedsurface is dried in air and irradiated with 'y-ray at a dose of 1.3 10Gr. (in the case of silicone resin 1.0 106 r.) under nitrogen atmospherehaving a humidity of 100% at 20 C.

The peel off strength in FIGS. 6 and 7 was determined as follows.

When the peel off load is less than 300 g./cm., an adhesive tape havingan adhesive strength of more than 300 g./cm. is adhered to the collagenlayer coated on the synthetic high polymer sheet material and a load isapplied to the tape and the load when the collagen layer is peeled ofifrom the sheet material is read.

When the peel off load is more than 300' g./cm., the collagen layercoated on said sheet material is adhered to a glass plate with siliconeadhesive and the load when said sheet material is peeled off from thecollagen layer is read.

As seen from FIGS. 6 and 7, the adhesion of the collagen layer to thesheet material which has been treated with the process of the presentinvention, is very high in the case of polyethylene and silicone resin,while polyethylene terephthalate and Teflon show a peel off strength ofabout 50 to 100 g./cm. but when these polymeric sheet materials coatedwith the collagen layer are dipped in water or physiological saltsolution for a long time, the collagen is not dissolved off nor peeledoff `and the practically satisfactory effect can be obtained.

When the artificial blood vessel made of polyethylene terephthalatefibers is coated with collagen by the process of the present invention,collagen penetrates into the space between fibers and coats the fibersand consequently the danger of peeling off is less than the coating of asheet material.

As mentioned above, in the process of the present invention, a diluteacid, such as hydrochloric acid, acetic acid and the like is used in theacidic aqueous solution of collagen, so that the coated collagen layercontains an acid. Accordingly, it is desirable to neutralize the acidand to remove the resulting salt from the collagen layer. Theneutralization and removal of salt may be effected either before orafter the third step but a sterilization effect can be attained by theirradiation of radioactive rays in the third step, so that it ispreferred to effect the neutralization and removal of salt before thethird step, because the resulting product is used in direct contact withliving body.

An explanation will be made with respect to the effect attained by theprocess of the present invention.

As mentioned above, the process of the present invention consists of thefirst, second and third steps and through each step, V( 1) the adhesionbetween collagen and the surface of shaped articles composed ofsynthetic high polymers increases, (2) the strength increases due to thecross-linking of collagen, (3) the compatibility with living bodyincreases and (4) the sterilization effect can be obtained.

Accordingly, the medical articles to be used in living body, which iscomposed of synthetic high polymers coated with collagen have a highadhesion between the collagen layer and the surface of the synthetichigh polymeric material and have a compatibility with living body, aresistance to coagulation of blood and an affinity to living body andcan be used directly without effecting sterilization operation after themanufacture. Furthermore, the process of the present invention consistsof technically simple steps and the practice is efficient and economicalThe following examples are given in illustration of this invention andare not intended as limitations thereof. In the example, percent meanspercent by weight.

EXAMPLE 1 After a surface of a silicone resin sheet was washed withacetone and then with hot water, the sheet was dried in air. A sparkdischarge having a spark length of 4 cm. was applied to the surface inair by means of a spark discharge generator (supply voltage AC 100 v.;input current 0.1-0.8 a.; frequency 50-100 kc.; spark length 1-5 cm.).During the discharge, the end of spark was always moved so as to applythe discharge uniformly as far as possible to the entire surface, andthe discharge time was 3 sec/cm?. Then, the surface of the sheet waseasily wettable.

A 0.5% acidic aqueous solution of collagen (N/400- HC1) was applied onthe surface of the above treated sheet, and the sheet was dried in airat 30 C. After dried, the sheet was dipped in a 1% aqueous solution ofNH4OH for about 1 hour to neutralize the collagen layer, dipped in coldwater 3 times to remove salt, and again dried in air at 30 C.

The sheet was irradiated with y-rays 'of 1.0 10e roentgens at 20 C.under 100% humidity and gaseous nitro- `gen atmosphere.

The surface of the resulting silicone resin sheet was tightly coatedwith a collagen layer in a thickness of about 6,1. T'he collagen layerwas not peeled off in a peel off test by means of an adhesive tape. Evenafter the sheet was dipped in water for 10 days, collagen was notdissolved out in water.

EXAMPLE 2 After the inner and outer surfaces of a silicone resin tubewere cleaned in the same manner as described in Example 1, a metalconductor was placed in the tube and a spark discharge having a sparklength of 4 cm. was applied to the tube from the outer surface of thetube in air by means of the spark discharge generator used in Example 1.When the end of spark was moved only along the longitudinal direction ofthe tube during the discharge, the inner and outer surfaces of the tubewere discharged with spark.The discharge time was 6 sec/cm?. Then, boththe inner and the outer surfaces of the tube were easily wettable.

The tube was dipped wholly in a 0.5% acidic aquels solution of collagenl(N/400-HC1), deaired so as not to remain bubbles in the interior of thetube, taken out from the solution and dried in air at 30 C. Since thetube was suspended and dried, the collagen solution applied on the tubefell down dropwise during the drying. The tube was again dipped in thesame collagen solution, taken out from the solution and dried at 30 C.

The tube was irradiated with 'y-rays in the same manner as described inExample l.

The surfaces of the resulting silicone resin resin tube were tightlycoated with a collagen layer in a thickness of about 6p. The collagenlayers were not peeled off in a peel off test by means of an adhesivetape. Even after the tube was dipped in water for 10 days, collagen wasnot dissolved out in water.

EXAMPLE 3 After a surface of a silicone resin sheet was washed withethanol and then with hot water, the sheet was dried in air. A sparkdischarge having a spark length of '3 cm. was applied to the surface inair by means of the spark discharge generator used in Example 1. Thedischarge time was 4 sec./cm.2. Then, the surface of the sheet waseasily wettable.

A 1% acidic aqueous solution of collagen (0.05% CH3CO0-H) was applied onthe surface of the above treated sheet, and the sheet was dried in airat 30 C. After the drying, the sheet was allowed to stand for 1 hour ina gaseous ammonia stream to neutralize the collagen layer, dipped indistilled water for 24 hours to remove salt, and dried at 30 C.

Then, the sheet was irradiated with an electron beam of 1.5 Mev. and4100 na. in a dose of 1.2X l06 r. by means of a Van de `Graaffelectrostatic accelerator under an atmosphere of humidity.

The surface of the resulting silicone resin sheet was tightly coatedwith a collagen layer in a thickness of about 10p. The collagen layerwas not peeled off in a peel off test by means of an adhesive tape. Evenafter the sheet was dipped in water for 10 days, collagen was notdissolved out in water.

EXAMPLE 4 The procedure described in Example 3 was repeated, except thatan ultraviolet ray was irradiated instead of the electron beam used inExample 3.

That is, a silicone resin sheet was irradiated with an ultraviolet rayin air at 30 C. and under 100% humidity from a distance of 10 cm. for1.5 hours by means of 4 w. ultraviolet ray sterlization lamp having amain peak of spectrum at 2,537 A.

The surface of the resulting silicone resin sheet was tightly coatedwith a collagen layer in a thickness of about 10u. The collagen layerwas not peeled off in a peel off test by means of an adhesive tape. Evenafter the sheet was dipped in water for l days, collagen was notdissolved out in water.

EXAMPLE A commercially available artificial blood vvessel made ofpolyethylene and that made of polypropylene were treated in thisexample. That is, after the inner and outer surfaces of the artificialblood vessel were washed with acetone and then with hot water, the bloodIvessel was dried in air. A metal conductor was placed in the vessel anda spark discharge having a spark length of 4 cm. was applied to thevessel from the outer surface of the vessel in air by means of the sparkdischarge generator used in Example 1. When the end of spark was movedonly along the longitudinal direction of the vessel during thedischarge, the inner and outer surfaces of the vessel were dischargedwith spark. The discharge time was 6 sec/cm?. Then, both the inner andouter surfaces of the blood vessel were easily wettable.

The above treated blood 'vessel was dipped wholly in a 0.1% acidicaqueous solution of collagen (N/400-HC1), deaired completely, taken outfrom the solution, and dried in air at 30 C. This process was repeated 3times.

The vessel was irradiated with ly-rays of 5 10 roentgens in air under100% humidity.

Each of the resulting artificial blood vessels was coated with acollagen layer in an average thickness of 2u. Even after the vessel wasdipped in water for 7 days, collagen was not dissolved out in water.

EXAMPLE =6 After the inner surface of a commercially available bloodcontainer made of polyethylene was cleaned in the same manner asdescribed in Example 5, a spark discharge having a spark length of 4 cm.was applied to the inner surface of the container in air by means of thespark discharge generator used in Example 1. During the discharge, theend of spark was always moved in the container so as to apply thedischarge uniformly as far as possible to the entire inner surface ofthe container. The discharge time was 5 sec./cm.2. Then, the innersurface of the blood container was easily wettable.

A 0.5% acidic aqueous solution of collagen (N/400-HC1) was charged intothe above treated blood container. After the solution was removed fromthe container, the container was draft dried at 30 C. and a 1% aqueoussolution of NH4OH was charged into the container to neutralize thecollagen layer. One hour later, the NHiOH solution was removed from thecontainer, and then the interior of the container was washed withdistilled water to remove salt, and the container was again dried.

The container was irradiated with 'y-rays of l.0 l06 roentgens at 20 C.under 100% humidity and gaseous nitrogen atmosphere.

The inner surface of the resulting blood container was coated with acollagen layer in an average thickness of 6u. Elven after the containerwas dipped in water for 10 days, collagen was not dissolved out inwater.

EXAMPLE 7 After an artificial blood vessel made of polyethyleneterephthalate fibers was washed with water thoroughly and dried, a sparkdischarge having a spark length of 3 cm. was applied to the vessel inthe samev manner as described in Example 2 by means of the sparkdischarge 10 generator used in Example 1. Then, the artificial bloodvessel was easily wettable.

The above treated artificial blood vessel was dipped wholly in a 0.2%acidic aqueous solution of collagen (N/400-HC1), deaired under reducedpressure to penetrate the collagen completely bet-Ween the fibers, takenout from the solution, and draft dried at 30 C. This process wasrepeated 2 times.

The vessel was irradiated with y-rays in the exactly same manner asdescribed in Example 1.

Even after the resulting artificial blood vessel was dipped in water for10 days, the coated collagen layer was not peeled off.

EXAMPLE 8 A Tefion sheet was treated in the same manner as described inExample 3 to coat the surface of the Teflon sheet with a collagen layerhaving a thickness of about 10/2.

A peel off test by an adhesive tape showed that the resulting sheet hada peel off strength of 50 g./cm. However, even after the sheet wasdipped in Water for 10 days, the collagen layer was not peeled off.

What is claimed is:

1. A method of manufacturing medical articles composed of a synthetichigh polymer coated with collagen and to be used in a living body, inwhich la surface of shaped articles composed of synthetic high polymersselected from the group consisting of polyethylene, polypropylene,polyethylene terephthalate and polytetrauoroethylene,

is subjected in an oxygen-containing atmosphere to a spark dischargewherein the product of the spark length in centimeters and the-discharge time per square centimeter is in the range of 9-12 cm.sec/cm?,

the thus treated surface is coated with an acidic aqueous solution ofcollagen and then dried at a temperature lower than the denaturationtemperature of collagen to form collagen layer and the shaped articlecoated with collagen layer is irradiated with gamma ray or electron beamto a dosage of l-5 10i r. or the equivalent dosage of ultraviolet light.

under an atmosphere having such a humidity that the water content of thecoated collagen becomes more than 20% by weight, to fix the collagenlayer.

2. The method as claimed in claim 1, wherein said gamma rays, electronbeam or ultraviolet ray is irradiated under an atmosphere having ahumidity of more than 75%.

3. The method as claimed in claim 1, wherein said radioactive rays,electron beam or ultraviolet ray is irradiated in water.

4. The method as claimed in claim 1, wherein said shaped article is afilm, pipe, tube, fiber, sponge or container.

5. The method as claimed in claim 1, wherein the acid in the acidicaqueous solution of collagen is neutralized and the resulting salt isremoved by washing with water.

6. The method as claimed in claim 1, wherein said neutralization andremoval of the salt are effected prior to the irradiation of gamma rays,electron beam or ultraviolet ray.

7. A method of manufacturing medical articles composed of a synthetichigh polymer coated 'with collagen to be used in a living body, in whicha surface of a shaped articles of film, pipe, tube, fiber or containercomposed of a synthetic high polymer selected from the group consistingof polyethylene, polypropylene, polyethylene terephthalate, andpolytetrafluoroethylene.

is subjected in an oxygen-containing atmosphere to a spark discharge of9-12 cm. see/cm.2 as determined from the spark length in centimeters andthe discharge time, per square centimeter,

1 l 1 Z the thus treated surface is coated with an acidic aque-References Cited ous solution of collagen and then dried at a temperavUNITED STATES PATENTS ture lower than the denaturation temperature ofcollagen to form a Collagen layer, Bennett et al.

the acid in the collagen layer is neutralized, the re. 5 3,700,57310/,1972 Laizier et al. zwi-159.13

sulting salt is removed by washing with water, and v the shaped articlecoated with collagen layer is JOHN C' BLEUTGE ,Primary Eammef irradiatedwith gamma rays or electron beam in a R B, TURER, Assistant Examinerdose of 15 106 r. or the equivalent dosages of ultraviolet light, 10U.S. Cl. X.R.

under an atmosphere having such a humidity that the Water ycontent ofthe coated collagen becomes more 3818 1388 UF than 20% by Weight, to xthe collagen layer.

